groupBy<S, T> method

Map<T, List<E>> groupBy<S, T>(
  1. T key(
    1. E
    )
)

Implementation

Map<T, List<E>> groupBy<S, T>(T Function(E) key) {
  var map = <T, List<E>>{};
  for (var element in this) {
    (map[key(element)] ??= []).add(element);
  }
  return map;
}